Effect of wheat dried distillers grains with solubles and fibrolytic enzymes on ruminal fermentation, digestibility, growth performance, and feeding behavior of beef cattle

Two experiments were conducted to evaluate the effect of wheat dried distillers grains with solubles (DDGS) and fibrolytic enzymes (FE) on ruminal fermentation, in situ ruminal and in vivo total tract digestibility, growth performance, and feeding behavior of growing beef cattle. In Exp. 1, 6 ruminally cannulated Angus heifers (average BW of 794 +/- 44.2 kg) were used in a 6 x 6 Latin square design with 2 x 3 factorial arrangement of treatments. Treatments were a control diet consisting of 50% barley silage, 10% grass hay, and 40% barley grain-based concentrate (CON) and the CON with 15% DDGS substituted for barley grain (WDG) combined with either 0, 1, or 2 mL FE/kg diet DM, respectively. Inclusion of DDGS increased total tract digestibility of CP (P < 0.01), NDF (P = 0.04), and ADF (P = 0.03). Increasing FE linearly (P = 0.03) increased CP digestibility without affecting the digestibility of other nutrients. There were no effects of DDGS inclusion or FE on ruminal pH or VFA concentration except that propionate was greater (P = 0.04) with the WDG. In situ ruminal DM and NDF disappearance of barley silage was greater (P < 0.04) in heifers fed the WDG than in heifers fed the CON after 24 h of incubation. Increasing FE linearly (P = 0.03) increased in situ NDF disappearance of barley silage after 24 h of incubation. In Exp. 2, 120 weaned steers (initial BW of 289 +/- 11.0 kg) were fed diets similar to those in Exp. 1. The steers fed the WDG had greater (P < 0.01) final BW, ADG, DMI, and G:F compared with steers fed the CON. Increasing FE did not alter ADG or G: F but tended (P < 0.07) to linearly decrease DMI. There were interactions (P < 0.02) between DDGS and FE on eating rate and the time spent at the feed bunk. Supplementing FE decreased (P < 0.01) time at the bunk and increased (P < 0.01) eating rate for steers fed the WDG but not for steers fed the CON. Eating rate (P < 0.01) and meal frequency (P = 0.02) were greater but eating duration was shorter (P < 0.01) for steers fed the WDG than for those fed the CON. These results indicate that inclusion of wheat DDGS in a growing diet increased total tract digestibility of NDF and CP and improved the feed efficiency of steers. Moreover, supplementation of FE in barley silage-based growing diets may also have the potential to increase profits, with the evidence of the trend for a decline on DMI without decreasing ADG when adding FE.